Thirty people were killed and 20 others injured after Boko Haram militants attacked three villages in northeastern Nigeria, Agence France-Presse (AFP) reported late Tuesday, citing a civilian helping the national army. According to the report, the militant group slaughtered the victims and set the villages on fire.

Mustapha Karimbe, a civilian helping the Nigerian military fight the Sunni militant group, reportedly said that the attacks were carried out in Warwara, Mangari and Bura-Shika in Borno state over the weekend.

"Most of the victims were slaughtered and most of the wounded [had suffered] machete cuts," Karimbe said, according to AFP.

Musa Suleiman, another witness, reportedly said that most of the victims were killed in Warwara. Attackers killed 20 people in Warwara, six in Bura-Shika and another four in Mangari, he added.

The villages are located near Buratai, about 130 miles southwest of Borno state capital Maiduguri. Buratai -- the hometown of the Nigerian Chief of Army Staff Lt. Gen. Tukur Yusuf Buratai -- and other nearby villages have recently been the targets of deadly attacks by Boko Haram militants, who have killed scores of people and looted the villages.

According to a recent report, Boko Haram militants have killed more people than the Islamic State group, also known as ISIS. Boko Haram was responsible for 6,664 deaths last year, much higher than any other terrorist group in the world. Iraq, Syria and Nigeria witnessed the most deaths, according to the report. ISIS to which Boko Haram pledged allegiance in March, killed 6,073 people last year.

Last week, Boko Haram militants reportedly killed 14 people -- decapitating some of them -- when they raided Kamuya village in Borno state and burnt it down.

Boko Haram, which aims to establish an ISIS-style government in northern Nigeria, has killed thousands of people since launching a brutal insurgency in the country six years ago.

Nigeria's government has vowed to end the Boko Haram insurgency by this month but attacks from the group continue, despite several efforts to end its violence.